SCHED_RR_GET_INTERVAL(2)  (2017-09-15)   SCHED_RR_GET_INTERVAL(2)

     NAME
          sched_rr_get_interval - get the SCHED_RR interval for the
          named process

     SYNOPSIS
          #include <sched.h>

          int sched_rr_get_interval(pid_t pid, struct timespec *tp);

     DESCRIPTION
          sched_rr_get_interval() writes into the timespec structure
          pointed to by tp the round-robin time quantum for the pro-
          cess identified by pid. The specified process should be run-
          ning under the SCHED_RR scheduling policy.

          The timespec structure has the following form:

              struct timespec {
                  time_t tv_sec;    /* seconds */
                  long   tv_nsec;   /* nanoseconds */
              };

          If pid is zero, the time quantum for the calling process is
          written into *tp.

     RETURN VALUE
          On success, sched_rr_get_interval() returns 0.  On error, -1
          is returned, and errno is set appropriately.

     ERRORS
          EFAULT
               Problem with copying information to user space.

          EINVAL
               Invalid pid.

          ENOSYS
               The system call is not yet implemented (only on rather
               old kernels).

          ESRCH
               Could not find a process with the ID pid.

     CONFORMING TO
          POSIX.1-2001, POSIX.1-2008.

     NOTES
          POSIX systems on which sched_rr_get_interval() is available
          define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

     Page 1                        Linux             (printed 5/24/22)

     SCHED_RR_GET_INTERVAL(2)  (2017-09-15)   SCHED_RR_GET_INTERVAL(2)

        Linux notes
          POSIX does not specify any mechanism for controlling the
          size of the round-robin time quantum.  Older Linux kernels
          provide a (nonportable) method of doing this.  The quantum
          can be controlled by adjusting the process's nice value (see
          setpriority(2)).  Assigning a negative (i.e., high) nice
          value results in a longer quantum; assigning a positive
          (i.e., low) nice value results in a shorter quantum.  The
          default quantum is 0.1 seconds; the degree to which changing
          the nice value affects the quantum has varied somewhat
          across kernel versions.  This method of adjusting the quan-
          tum was removed starting with Linux 2.6.24.

          Linux 3.9 added a new mechanism for adjusting (and viewing)
          the SCHED_RR quantum: the
          /proc/sys/kernel/sched_rr_timeslice_ms file exposes the
          quantum as a millisecond value, whose default is 100.  Writ-
          ing 0 to this file resets the quantum to the default value.

     SEE ALSO
          sched(7)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

     Page 2                        Linux             (printed 5/24/22)